Electronic braking arrangements

ABSTRACT

An electronic braking arrangement includes a brake stack assembly, a driver circuit, a current limiter circuit, and a voltage limiter circuit. The driver circuit is operably connected to the brake stack assembly. The current limiter circuit and the voltage limiter circuit are connected in series between the driver circuit and the brake stack assembly to drive friction brake loads in the brake stack assembly with a voltage limited constant drive current.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present disclosure relates to braking, and more particularly toelectronic braking arrangements such as in aircraft landing gearsystems.

2. Description of Related Art

Vehicles, such as aircraft, commonly have electrically actuated brakingsystems. The braking system typically includes an actuation circuitoperable to move a friction pad into contact with a rotor. The rotor isgenerally fixed relative to a wheel and rotatable relative to thefriction pad such that, upon actuation, the friction pad comes intocontact with the rotor to resist rotation of the rotor and the wheel.The brake stack typically includes a solenoid or coil that is arrangedto receive an actuation current from a current source. The actuationcurrent generates an electromagnetic force that drives the friction padinto frictional engagement with the rotor, the friction pad therebyopposing rotation of the rotor and wheel assembly.

In some braking systems the rotor includes a set of locking frictionpads arranged as a brake stack. Two or more solenoids or coils areoperable to cooperatively move the friction pads into frictionalengagement with the rotor, typically by receiving proportions of adriver current applied to the brake stack by the driver circuit. Thesolenoids or coils are typically connected to the actuation currentsource in parallel with one another such that the portion of theactuation current corresponds to the resistance of the respectivesolenoid or coil.

Such conventional methods and systems have generally been consideredsatisfactory for their intended purpose. However, there is still a needin the art for improved driver circuits, braking systems, and methods ofengaging and disengaging brakes in aircraft landing gear systems. Thepresent disclosure provides a solution to this need.

SUMMARY OF THE INVENTION

An electronic braking arrangement includes a brake stack assembly, adriver circuit, a current limiter circuit, and a voltage limitercircuit. The driver circuit is operably connected to the brake stackassembly. The current limiter circuit and the voltage limiter circuitare connected in series between the driver circuit and the brake stackassembly to drive friction brake loads in the brake stack assembly witha voltage limited constant drive current.

In certain embodiments, electronic braking arrangement can be a parkingbrake arrangement. The brake stack assembly can include two or moreelectrical loads connected electrically in parallel with each other. Thetwo or more electrical loads can include coils or windings. The coil orwindings of each electrical load can be operably connected to individualfriction pads of the brake assembly. The brake stack assembly caninclude four electrical loads operably connected to four friction padsin a landing gear rotor/wheel arrangement.

In accordance with certain embodiments, the driver circuit can bearranged to issue a slowly ramping voltage pulse. The slowly rampingvoltage pulse can be issued to the stack assembly through the drivercircuit and current limiter circuit to actuate the brake stack assembly.The driver circuit can include a source lead, a return lead, and acontrol lead. The source lead can be connected by the driver circuit tothe current limiter circuit. The return lead can connect the voltagelimiter circuit to a ground terminal through the driver circuit. Thedriver circuit can include a solid-state switch connected in seriesbetween the source lead and the current limiter circuit. The controllead can be operably connected to the solid-state switch.

It is contemplated that the current limiter circuit can include a firstresistor leg and a second resistor leg. The first resistor leg can havea solid-state switch. The switch can be an insulated gate bipolartransistor (IGBT) with a collector and an emitter. A reference voltagesource can be connected between the brake assembly and the IGBT emitter.First and second resistors can be connected in series with one anotherand between the IGBT collector and the current limiter circuit. Thefirst resistor can have a resistance that is greater than the resistanceof the second resistor.

It is also contemplated that, in accordance with certain embodiments,the second resistor leg can include a switch device. The second resistorleg switch device can be a MOSFET with source, a drain, and a gate. Aresistor can be connected in series with the MOSFET source and betweenthe MOSFET and the current limiter circuit. A diode can be connected inseries with the MOSFET drain and between the brake stack assembly andthe MOSFET. The diode can be arranged to oppose current flow from thebrake stack assembly to the MOSFET. The IGBT can be a first IGBT and thecurrent limiter circuit can include a second IGBT. An emitter of thesecond IGBT can be connected to the second resistor leg. A collector ofthe second IGBT can be connected to the first resistor leg.

In further embodiments the voltage limiter circuit can include a MOSFET.The MOSFET can be connected in series between the brake stack assemblyand the current limiter circuit. A gate of the MOSFET can be connectedto the return lead. A drain of the MOSFET can be connected to thecurrent limiter circuit. A gate of the MOSFET can be connected to thereturn lead. First and second Zener diodes can be connected in serieswith one another and in parallel with a capacitor between the sourcelead and the return lead.

These and other features of the systems and methods of the subjectdisclosure will become more readily apparent to those skilled in the artfrom the following detailed description of the preferred embodimentstaken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject disclosureappertains will readily understand how to make and use the devices andmethods of the subject disclosure without undue experimentation,embodiments thereof will be described in detail herein below withreference to certain figures, wherein:

FIG. 1 is a block diagram of an exemplary embodiment of an electronicbraking arrangement for an aircraft landing gear system constructed inaccordance with the present disclosure, showing driver circuit connectedto a brake stack assembly through a current limiter circuit and avoltage limiter circuit;

FIG. 2 is a circuit schematic of the brake stack assembly of FIG. 1,showing parallel electrical loads operably connected to friction pads ofa rotor/wheel assembly;

FIG. 3 is a circuit schematic of the driver circuit of FIG. 1, showing asolid-state switch connected to the source lead and operably connectedto a control lead for applying a slowing ramping actuation current tothe brake stack assembly;

FIG. 4 is a circuit schematic of the voltage limiter circuit of FIG. 1,showing parallel resistor legs with solid-state switches connectedbetween the current limiter circuit and the brake stack assembly forlimiting voltage applied to the brake stack assembly; and

FIG. 5 is a circuit schematic of the current limiter circuit of FIG. 1,showing a switch and Zener diodes connected in parallel with a capacitorbetween the source and return leads for maintaining constant currentflow through the brake stack assembly electrical loads irrespective ofresistance change in one or more of the electrical loads.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawings wherein like referencenumerals identify similar structural features or aspects of the subjectdisclosure. For purposes of explanation and illustration, and notlimitation, a partial view of an exemplary embodiment of an electronicbraking arrangement in accordance with the disclosure is shown in FIG. 1and is designated generally by reference character 100. Otherembodiments of electronic braking arrangements and methods of actuatingelectronic braking arrangements in accordance with the disclosure, oraspects thereof, are provided in FIGS. 2-5, as will be described. Thesystems and methods described herein can be used to implement parkingbrake functionality in aircraft landing gear, though the presentdisclosure is not limited to parking brake functionality to aircraftlanding gear systems in general.

Referring to FIG. 1, electronic braking arrangement 100, e.g., a parkingbrake arrangement for an aircraft landing gear system, is shown.Electronic braking arrangement 100 includes a driver circuit 102, acurrent limiter circuit 104, a voltage limiter circuit 106 with avoltage limit 107, and a brake stack assembly 108. Driver circuit 102 isoperably connected to brake stack assembly 108. Current limiter circuit104 and voltage limiter circuit 106 are connected electrically in serieswith one another between driver circuit 102 and brake stack assembly 108to actuate brake friction pads, e.g., a friction pad 124 (shown in FIG.2), in a rotor/wheel assembly 10 with a voltage-limited constant drivecurrent, e.g., drive current 14 (shown in FIG. 2). Voltage limit 107 isselected such that drive current 14 applied to brake stack assembly 108can rise to a predetermined value in response to resistance increase,and thereafter remains constant as resistance further increases.

With reference to FIG. 2, brake stack assembly 108 is shown. Brake stackassembly 108 includes a source lead 110, a return lead 112, and a brakestack 114. Brake stack 114 includes a plurality of electrical loads116-122 that are operatively coupled to friction pads 124-130. Frictionpads 124-130 are each movable between a disengaged position A, whereinfriction pads 124-130 are spaced apart from a rotor 12 of rotor/wheelassembly 10 (shown in FIG. 1), and an engaged position B, whereinfriction pads 124-130 being in frictional contact with rotor 12 in theengaged position. Movement of the respective friction pads 124-130occurs when current flow through electrical loads 116-122, e.g., a coilsor windings connected in series with a respective resistor, exceeds aselected value.

In the illustrated exemplary embodiment brake stack 114 includes a firstelectrical load 116 with an inductor connected in series with aresistor, a second electrical load 118 with an inductor connected inseries with a resistor, a third electrical load 120 with an inductorconnected in series with a resistor, and a fourth electrical load 122with an inductor connected in series with a resistor. First electricalload 116 is connected between source lead 110 and return lead 112 and isoperably connected to a first friction pad 124. Second electrical load118 is connected between source lead 110 and return lead 112, isconnected electrically in parallel with first electrical load 116, andis operably connected to a second friction pad 126. Third electricalload 120 is connected between source lead 110 and return lead 112, isconnected electrically in parallel with second electrical load 118, andis operably connected to a third friction pad 128. Fourth electricalload 122 is connected between source lead 110 and return lead 112, isconnected electrically in parallel with third electrical load 120, andis operably connected to a fourth friction pad 130. Although electronicbraking arrangement 100 is described herein as having four electricalloads comprising coils or windings, it is to be understood andappreciated electronic braking arrangement 100 can have fewer than ormore than four electrical loads, including non-coil or windingelectrical loads, as suitable for an intended application.

During actuation driver circuit 102 (shown in FIG. 1) applies drivecurrent 14 to brake stack 114 through source lead 110. Drive current 14flows through each of the parallel windings or coils in a proportionthat corresponds to the relative resistance of each of the coils orwindings of electrical loads 116-122. In embodiments where theelectrical resistance of each electrical load, e.g., electrical loads116-122, are substantially equivalent to one another, current flows16-22 through each of the electrical loads is substantially equivalentto that through the other electrical loads. For example, in theillustrated exemplary embodiment, current flow 16 is about one quarterof drive current 14, current flow 18 is about one quarter of drivecurrent 14, current flow 20 is about one quarter of drive current 14,and current flow 22 is about one quarter of source current flow 14. Aswill be appreciated by those of skill in the art in view of the presentdisclosure, equivalent proportioning of drive current 14 amongelectrical loads 116-122 provides synchronous movement of friction pads124-130 between the engaged position A and disengaged position Brelative to rotor 12.

As will be also appreciated by those of skill in the art in view of thepresent disclosure, resistance increase in a given electrical load canincrease the proportion of current flowing through the other electricalloads. For example, if third electrical load 120 develops an open 132(indicated with an exemplary with dotted segment of third electricalload 120), magnitudes of current flows 16, 18 and 22 can increase toabout one-third of drive current flow 14. The increased magnitudes ofcurrent flows 16, 18 and 22 in turn exerts additional current stress onthe remaining connected electrical loads (i.e. first electrical load116, second electrical load 118 and fourth electrical load 122),generating additional heat and potentially damaging one or more of theremaining connected electrical loads. For that reason, some electronicbraking arrangements employ electrical loads sized to accommodatecurrent flows well above that normally received to actuate a givenfriction pad. While generally satisfactory for its intended purpose,oversizing electrical loads in brake stack assemblies can add weight andcost to the brake stack assembly. To reduce (or eliminate entirely) theneed to oversize electrical loads 116-122 in brake stack 114 in theevent that one or more of electrical loads 116-122 increases inresistance or fails open, electronic brake arrangement 100 (shown inFIG. 1) includes current limiter circuit 104 (shown in FIG. 1) andvoltage limiter circuit 106 (shown in FIG. 1).

Current limiter circuit 104 and voltage limiter circuit 106 cooperate toadjust the current applied to brake stack 114 when resistance of one ormore electrical loads therein increases by correspondingly reducing themagnitude of drive current 14. In this respect voltage limit 107 (shownin FIG. 1) is selected to allow drive current 14 to rise to currentlimit (shown in dotted outline) in response to current supplied to theremaining electrical loads by reducing magnitude of drive current 14once current rises above a selected current value. For example, incertain embodiments, voltage limiter circuit 106 has a voltage limit 107(shown in FIG. 1). Voltage limit 107 that allows for increase in themagnitude of drive current 14 applied to electrical loads 116-122 suchthat current flow through any one of the electrical loads 116-122 canrise no more than about 30%. Once voltage rises to voltage limit 107current limiter circuit 104 decreases the magnitude of drive current 14thereafter applied to electrical loads 116-122 commensurate with furtherresistance increase in electrical loads 116-122. The subsequent decreasein drive current 14 causes the magnitude of current flows 16-22 toremain within the current rating of electrical loads 116-122notwithstanding subsequent resistance increase in electrical loads116-122, for example, by a second one of electrical loads 116-122becoming electrically open.

In an exemplary embodiment of landing gear arrangement 100 (shown inFIG. 1) electrical loads 116-122 are each rated for about 0.6 amps.Voltage limit 107 is selected such that electrical loads 116-122 eachreceive about 0.3 amps when resistance is equivalent among each ofelectrical loads 116-122, each electrical load 116-122 receive no morethan 0.4 amps when one or more than electrical loads 116-122 becomeelectrically open, and each electrical load 116-122 receive no more than0.4 amps when two or more of electrical loads 116-122 becomeelectrically open. This limits (or eliminates) the stress that otherwiseis exerted on the remaining electrical loads when one or more of theelectrical loads experiences a resistance increase (or becomes open) byallowing continued operation of the remaining electrical loads withinthe their respective current rating. Current limiter circuit 104 andvoltage limiter circuit 106 are also arrangement to cooperate withslowly ramping drive current 14, which reduces (or eliminates entirely)the need to harden electrical devices in proximity to electronic brakearrangement 100 to upset/crosstalk issues that can otherwise arise whenpulse width modulated (PWM) drive current are employed to actuate brakestack 114. As used herein, slowly ramping refers to drive currents thatrise to a selected threshold to actuate brake stack 114 is a timeinterval greater than that required by PWM signals, e.g., 10 kilohertzPWM drive current signals.

With reference to FIG. 3, driver circuit 102 is shown. Driver circuit102 includes a switch device 134, a transistor module 136, a controllead 138, source lead 110 and return lead 112. In the illustratedexemplary embodiment switch device 134 is a MOSFET device with a source140, a drain 142 and a gate 144. Transistor module 136 is connected todrain 142 through a Zener diode 146, which is arranged to oppose currentflow from gate 144 through a serially connected resistor 148. Drain 142is connected to current limiter circuit 104 (shown in FIG. 1) via asource lead input segment 161. Source 140 is connected to source lead110, and further to transistor module 136 through a serially connectedZener diode 150. Zener diode 150 is arranged to oppose current flow fromsource lead 110 to transistor module 136. In certain embodiments, Zenerdiode can be a P4SMA100A TVS diode, available from VishayIntertechnology of Malvern, Pa.

It is contemplated that switch device 134 be a power MOSFET arrangedwithin driver circuit 102 to operate as a linear regulator, the powerMOSFET thereby operating within the power MOSFET linear region.Operating as linear regulator, switch device 134 can potentiallyexperience high thermal stress due to the simultaneous occurrence ofhigh drain voltage and current, resulting in high power dissipation. Toalleviate (or prevent entirely) high thermal stress, the power MOSFETincorporated in switch device 134 has high power dissipation capabilityand an extended forward-bias safe operating area, the latter beingachieved by the power MOSFET suppressing positive feedback associatedwith electro thermal instability. Examples of suitable power MOSFETdevices for switch device 134 include IXTR32P60P MOSFET devices,available from IXYS Corporation of Milpitas, Calif.

Transistor module 136 is connected to control lead 138, return lead 112and a ground terminal 152. Examples of suitable transistor modulesinclude CPC1302 transistor modules, available from IXYS IntegratedCircuits Division of Beverley Massachusetts. In certain embodimentscontrol lead 138, source lead 110, and return lead 112 are connected toDC power sources, control lead 138 receiving logic signals therethroughto actuate brake stack assembly 108 (shown in FIG. 1), source lead 110and return lead 112 being connected to a DC power source for selectiveapplication of power therefrom to brake stack assembly 108. In anexemplary embodiment control lead 138 is connected to a 5 volt DC powersource for receiving a logical on/off control signal, and source lead110 and return lead 112 are respectively connected to positive andnegative terminals of a 130 volt DC power source for energizingelectrical loads 116-122 (shown in FIG. 2) of brake stack assembly 108.

With reference to FIG. 4, current limiter circuit 104 is shown. Currentlimiter circuit 104 is connected in series with source lead 110, andtherethrough to driver circuit 102 (shown in FIG. 1), and includes afirst resistor leg 154, a second resistor leg 156, a switch device 158,and a diode 160. First resistor leg 154 and second resistor leg 156 areconnected in parallel with one another between a source lead inputsegment 161 and a source lead output segment 163. Switch device 158 anddiode 160 are connected to both first resistor leg 154 and secondresistor leg 156.

First resistor leg 154 includes a first resistor 162, a second resistor164, a switch device 166, and a reference voltage source 168. Firstresistor 162 is connected to source lead input segment 161 and secondresistor leg 156. Second resistor 164 is connected in series with firstresistor 162 and has a resistance that is smaller than a resistance offirst resistor 162, e.g., having a resistance that is about 5% theresistance of first resistor 162. Switch device 166 is connected inseries with second resistor 164 and includes an IGBT device with a gate170, an emitter 172, and a collector 174. Reference voltage source 168is connected in series with emitter 172 and source lead output segment163 and has an output voltage. In certain embodiment the output voltageis 1.0 volts. Examples of suitable reference voltage sources includeADR510 voltage sources, available from Analog Devices Inc. of Norwood,Mass. In accordance with certain embodiments switch device 166 can be a2N2222 IGBT device, available from ST Microelectronics of Geneva,Switzerland.

Second resistor leg 156 includes a switch device 176, a resistor 178,and a diode 180. Switch device 176 includes a MOSFET device with asource 182, a drain 184, and a gate 186, source 182 connecting to sourcelead output segment 163 and first resistor leg 154. Resistor 178 isconnected in series with drain 182 and diode 180. Diode 180 is connectedin series between resistor 178 and source lead output segment 163 and isarranged to oppose current flow from source lead output segment 163 toresistor 178. It is contemplated that diode 180 can be an SMLJ60S6diode, available from Micro Commercial Components, Inc. of Thief RiverFalls, Minnesota. The MOSFET included in switch device 176 can be apower MOSFET device arranged to operate as linear regulator andconfigured for high power dissipation capability and extendedforward-bias safe operating area. Examples of suitable power MOSFETdevices include IXTB30N100L Linear Power MOSFET devices, also availablefrom IXYS Corporation of Milpitas, Calif.

Zener diode 160 has an anode 188 and a cathode 190. Anode 188 isconnected to switch device gate 170 and second resistor leg 156,connection to second resistor leg 156 being at a location interposedbetween source 182 and resistor 178. Cathode 190 is connected to switchdevice gate 186 and first resistor leg 154, connection to first resistorleg 154 being at a location between first resistor 162 and secondresistor 164. Zener diode 1160 can be a P4SMA24A TVS diode, availablefrom Vishay Intertechnology of Malvern, Pa.

Switch device 158 is an IGBT device with a collector 192, an emitter 194and a gate 196. Collector 192 is connected to a lead 198 interconnectingfirst resistor leg 154, switch device gate 186, and Zener diode cathode190. Gate 196 is connected to first resistor leg 154 at a locationbetween second resistor 164 and collector 174. Emitter 194 is connectedto a lead 101, which interconnects emitter 194 with gate 170 of switchdevice 166, Zener diode anode 188, and second resistor leg 156 at alocation between switch device 176 and resistor 178. Switch device 158can include a 2N2907 IGBT device, available from ST Microelectronics ofGeneva, Switzerland.

With reference to FIG. 5, voltage limiter circuit 106 is shown. Voltagelimiter circuit 106 interconnects source lead 110 with return lead 112and includes a first branch 103, a second branch 105 with a freewheelingor flyback diode 125, and a switch device 127. Freewheeling or flybackdiode 125 is arranged to oppose current flow from source lead 110 toreturn lead 112. Switch device 127 includes a MOSFET device arranged asa linear regulator and is connected in series with source lead 110between current limiter circuit 104 (shown in FIG. 1) and brake stackassembly 108 (shown in FIG. 1). Switch device 127 can include anIXTX22N100L Linear Power MOSFET device, also available from IXYSCorporation of Milpitas, Calif.

First branch 103 includes a capacitor 109, first Zener diode 111, and asecond Zener diode 113. Second Zener diode 113 is connected in serieswith first Zener diode 111, serially connected first Zener diode 111 andsecond Zener diode 113 both being arranged to oppose current from sourcelead 110 to return lead 112. Capacitor 109 is connected in parallel withserially connected first Zener diode 111 and second Zener diode 113,positive and negative charge plates of capacitor 109 being connected tosource lead 110 and return lead 112, respectively. The negative chargeplate of capacitor 109 connects directly to return lead 112 and theanode of second Zener diode 113.

The positive charge plate of capacitor 109 connects to source lead 110through a resistor 115, and is further connected to the cathode of firstZener diode 111, a gate of switch device 127 via an intervening resistor119, and to a source of switch device 127 via resistor 115 and a Zenerdiode 117. Zener diode 117 is arranged to oppose current flow fromresistor 115 to source lead 110. First Zener diode 111 can be a P4SMA56Adiode, available from Vishay Intertechnology of Malvern, Pa. SecondZener diode 113 can be a P4SMA24A TVS diode, also available from VishayIntertechnology of Malvern, Pa.

Friction brake driver electronics commonly employ friction brake driverelectronics with pulse width modulated drive currents to actuate theassociated friction brake. Examples of such driver electronics includethe EBAC-5 friction brake driver electronics unit, available fromSimmonds Precision Products, Inc. of Vergennes, Vt. While satisfactoryfor its intended purpose, the 10 kilohertz 50% PWM drive achieved bysquare wave modulation of the DC link voltage employed by such systemscan impose electrical shielding requirements on electrical devices inproximity to the driver electronics due to associated radio-frequencyemissions.

In certain embodiments described herein, electronic braking arrangement100 includes a non-PWM driver circuit 102. Driver circuit 102 isarranged to apply a constant drive current, e.g., drive current 14(shown in FIG. 3), that is voltage limited by a voltage limit 107 (shownin FIG. 1) to drive a parallel combination of friction brake padslocated in a brake stack assembly 108 (shown in FIG. 2). It iscontemplated that drive current 14 ramp slowly (relative to the rate ofchange in a PWM drive signal), thereby reducing (or eliminating)emissions that could otherwise impose a requirement for shielding due toupset/crosstalk between the friction brake driver circuit and circuitryin proximity to the river circuit, such as resolver circuitry, which canalso operate at frequencies around 10 kilohertz.

In accordance with certain embodiments described herein, electronicbraking arrangement 100 includes current limiter circuit 104 and voltagelimiter circuit 106. Current limiter circuit 104 and voltage limitercircuit 106 cooperate to limit voltage applied to brake stack assembly108, thereby allowing voltage applied to source lead 110 and return lead112 to vary within a predetermined voltage range. It is contemplatedthat the selected range can be between 220 and 450 volts, enablingelectronic braking arrangement 100 to be retrofit into standardizedelectronic braking system.

Further, in certain embodiments electronic braking arrangement 100 iscurrent-limited. In this respect current limiter circuit 104 and voltagelimiter circuit 106 are arranged to limit current applied to eachparallel electrical load arranged within brake stack assembly 108. Thecurrent limiting is such that current can rise through each of theelectrical loads as resistance increases to a selected current magnitudethat is within the current rating the electrical loads. The currentthereafter remains constant notwithstanding further resistance increasein one or more of the electrical loads. For example, in a brake stackassembly with electrical loads rated for 0.6 amps, electronic brakingarrangement 100 limits flow through each electrical load to about 0.4amps or lower when one of the electrical load exhibits increasedelectrical resistance or becomes open, and thereafter causes currentflow through each electrical load to remain at about 04 ampsnotwithstanding a second or more of the electrical loads to become open.

It is also contemplated that current limiter circuit 104 and voltagelimiter circuit 106 be arranged to provide constant current in the eventof resistance change, for example, current flow through each connectedelectrical load remaining constant notwithstanding resistance changefrom heating. For example, current flow can remain constant within aresistance range of between about 50 ohms and 120 ohms, therebypreventing overcurrent stress from heating associated with friction padheating.

The methods and systems of the present disclosure, as described aboveand shown in the drawings, provide for electronic braking arrangementswith superior properties including drive current without PWM, constantcurrent, and/or variable voltage. While the apparatus and methods of thesubject disclosure have been shown and described with reference topreferred embodiments, those skilled in the art will readily appreciatethat change and/or modifications may be made thereto without departingfrom the scope of the subject disclosure.

What is claimed is:
 1. An electronic braking arrangement, comprising: abrake stack assembly; a driver circuit operably connected to the brakestack assembly; and a current limiter circuit and a voltage limitercircuit connected in series between the brake stack assembly to drivefriction brake loads in the brake stack assembly with a voltage limitedconstant drive current, wherein the brake stack assembly includes fourelectrical friction brake loads operably connected to four frictionpads.
 2. The electronic braking arrangement as recited in claim 1,wherein the brake stack assembly includes a plurality of electricalloads connected electrically in parallel with each other.
 3. Theelectronic braking arrangement as recited in claim 1, wherein the drivercircuit is arranged to issue a slowly ramping voltage pulse to the stackassembly through the driver circuit and current limiter circuit toactuate the brake stack assembly.
 4. The electronic braking arrangementas recited in claim 1, wherein the driver circuit includes a sourcelead, a return lead, and a control lead.
 5. The electronic brakingarrangement as recited in claim 4, wherein the source lead is connectedby the driver circuit to the current limiter circuit.
 6. The electronicbraking arrangement as recited in claim 4, wherein the return leadconnects the voltage limiter circuit to a ground terminal through thedriver circuit.
 7. The electronic braking arrangement as recited inclaim 4, wherein the driver circuit includes a solid-state switchconnected in series between the source lead and the current limitercircuit, wherein the control lead is operably connected to thesolid-state switch.
 8. An electronic braking arrangement, comprising: abrake stack assembly; a driver circuit operably connected to the brakestack assembly; and a current limiter circuit and a voltage limitercircuit connected in series between the brake stack assembly to drivefriction brake loads in the brake stack assembly with a voltage limitedconstant drive current, wherein the current limiter circuit includesfirst and second resistor legs each having switch devices.
 9. Anelectronic braking arrangement as recited in claim 8, wherein the firstresistor leg includes an IGBT device with a collector and emitter, areference voltage connected between the brake stack assembly and theIGBT emitter, and first and second resistors connected in series betweenthe current limiter circuit and the IGBT collector.
 10. The electronicbraking arrangement as recited in claim 8, wherein the second resistorleg includes a MOSFET with a source and a drain, resistor connected inseries with the MOSFET source, and a diode connected in series with theresistor, wherein the diode is arranged to oppose current flow from thebrake stack assembly to the MOSFET.
 11. The electronic brakingarrangement as recited in claim 8, further comprising an IGBT devicewith an emitter and connected to the second resistor leg and a collectorconnected to the first resistor leg.
 12. An electronic brakingarrangement, comprising: a brake stack assembly; a driver circuitoperably connected to the brake stack assembly; and a current limitercircuit and a voltage limiter circuit connected in series between thebrake stack assembly to drive friction brake loads in the brake stackassembly with a voltage limited constant drive current, wherein thevoltage limiter circuit includes a MOSFET connect in series between thebrake stack assembly and the current limiter circuit.
 13. The electronicbraking arrangement as recited in claim 12, wherein the MOSFET has agate, a source, and drain, wherein the gate is connected to the returnlead, wherein the source is connected to the brake stack assembly, andwherein the drain is connected to the current limiter circuit.
 14. Theelectronic braking arrangement as recited in claim 13, furthercomprising serially connected Zener diodes and a capacitor, wherein theserially connected Zener diodes and capacitor are connected in parallelwith one another between the source lead and the return lead.
 15. Anelectronic parking brake arrangement for a landing gear system,comprising: a landing gear wheel assembly with a rotor; an electronicbraking arrangement as recited in claim 1, wherein the brake stackassembly includes four electrical friction brake loads operablyconnected to four friction pads; wherein the four friction pads have adisengaged position and an engaged position, the friction pads beingspaced apart from the rotor in the disengaged position, the frictionpads being fixed against the rotor in the engaged position, wherein thedriver circuit is arranged to issue a slowly ramping voltage pulse tothe stack assembly through the driver circuit and current limitercircuit to actuate the brake stack assembly and move the friction padsbetween the disengaged and engaged positions.